docs: def com_google_fonts_check_vendor_id(ttFont, registered_vendor_ids):
    """Checking OS/2 achVendID."""
  
    SUGGEST_MICROSOFT_VENDORLIST_WEBSITE = (
      " You should set it to your own 4 character code,"
      " and register that code with Microsoft at"
      " https://www.microsoft.com"
    "/typography/links/vendorlist.aspx")
  
    vid = ttFont['OS/2'].achVendID
    bad_vids = ['UKWN', 'ukwn', 'PfEd']
    if vid is None:
      yield WARN, Message("not set", "OS/2 VendorID is not set." +
                                     SUGGEST_MICROSOFT_VENDORLIST_WEBSITE)
    elif vid in bad_vids:
      yield WARN, Message("bad", ("OS/2 VendorID is '{}',"
                                  " a font editor default.").format(vid) +
                                  SUGGEST_MICROSOFT_VENDORLIST_WEBSITE)
    elif vid not in registered_vendor_ids.keys():
      yield WARN, Message("unknown", ("OS/2 VendorID value '{}' is not"
                                      " a known registered id.").format(vid) +
                                      SUGGEST_MICROSOFT_VENDORLIST_WEBSITE)
    else:
      yield PASS, f"OS/2 VendorID '{vid}' looks good!"